212 research outputs found
X-ray spectral evolution of V404 Cygni in the initial phase of the 2015 outburst
The black hole binary GS 2023+338 exhibited an unprecedently bright outburst
on June 2015. Since June 17th, the high energy instruments on board INTEGRAL
detected an extremely variable emission during both bright and low luminosity
phases, with dramatic variations of the hardness ratio on time scales of
~seconds. The analysis of the IBIS and SPI data reveals the presence of hard
spectra in the brightest phases, compatible with thermal Comptonization with
temperature kTe ~ 40 keV. The seed photons temperature is best fit by kT0 ~ 7
keV, that is too high to be compatible with blackbody emission from the disk.
This result is consistent with the seed photons being provided by a different
source, that we hypothesize to be a synchrotron driven component in the jet.
During the brightest phase of flares, the hardness shows a complex pattern of
correlation with flux, with a maximum energy released in the range 40-100 keV.
The hard X-ray variability for E > 50 keV is correlated with flux variations in
the softer band, showing that the overall source variability cannot originate
entirely from absorption, but at least part of it is due to the central
accreting source.Comment: 5 pages, 4 figures, accepted for publication in Astrophysical Journal
Letter
Contribution of point sources to the soft gamma-ray Galactic emission
The nature of the soft gamma-ray (20-200 keV) Galactic emission has been a
matter of debate for a long time. Previous experiments have tried to separate
the point source contribution from the real interstellar emission, but with a
rather poor spatial resolution, they concluded that the interstellar emission
could be a large fraction of the total Galactic emission. INTEGRAL, having both
high resolution and high sensitivity, is well suited to reassess more precisely
this problem. Using the INTEGRAL core program Galactic Center Deep Exposure
(GCDE), we estimate the contribution of detected point sources to the total
Galactic flux.Comment: Proceedings of the 5th INTEGRAL Workshop, Munich 16-20 February 2004.
ESA SP-55
Flow Induced Pulsations (FLIP) in 6-inch rough bore gas flexible pipes Test
International audienceSince the beginning of the 21 st century FLow-Induced Pulsations (FLIP) has been more and more experienced. The phenomenon is characterized by an acoustic wave that is created inside of the flexible pipe and that may lead to significant fatigue failure of the adjacent equipment. Flexible pipe integrity is not called into question regarding this phenomenon. In this context, a FLIP joint test involving an Oil Company, a Flexible Pipe supplier and a French research center was conducted end of 2016 at French laboratory in Poitiers. The test was performed in a 6'' internal diameter and 18-meter-long flexible pipe. Both flow directions were tested to assess the influence of the rounded edges of the carcass. On the one hand, this paper presents the experimental test setup and the main results that came out of the test. On the other hand, this paper also presents the comparison between tests results and analytical model outcome. Moreover, combining experiments and theoretical point of view enabled reproducing the phenomenon. A better understanding of the phenomenon will allow flexible pipes suppliers to propose mitigations or cancellation of FLIP to companies
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